2 Answers
2

You can set the default with of NERDTree through NERDTreeWinSize, e.g. let NERDTreeWinSize = 1 in .vimrc. You can adjust the size of the windows through the normal VIM commands, see :help window-resize.

Check your settings for equalalways and eadirection, as they dictate what size new windows start out as. If equalalways is set, then all new windows will be created equal in width, height, or both, depending on the value of eadirection.

Also, the NERDTree setting: NERDTreeWinSize defaults to a width of 31 characters, you may want to adjust that (after checking the equalalways and eadirection options in vim too)